Hafnium–tungsten dating is a geochronological radiometric dating method utilizing the radioactive decay system of hafnium-182 to tungsten-182. The half-life of the system is 8.9±0.1 million years. Today hafnium-182 is an extinct radionuclide, but the hafnium–tungsten radioactive system is useful in studies of the early Solar System since hafnium is lithophilic while tungsten is moderately siderophilic, which allows the system to be used to date the differentiation of a planet's core. It is also useful in determining the formation times of the parent bodies of iron meteorites.
The use of the hafnium-tungsten system as a chronometer for the early Solar System was suggested in the 1980s, but did not come into widespread use until the mid-1990s when the development of multi-collector inductively coupled plasma mass spectrometry enabled the use of samples with low concentrations of tungsten.
